I simply cannot imagine the shower consistently sunny enough so as to ensure long term health of an orchid. Bsides which, showers, and by extension bathrooms, are way overrated as a place to grow orchids. The humidity advantage is only present when the shower is actually running. That is less than one hour per day total for an average American family. A kitchen, IMO is a way, way better place to grow in that it usually has all the advantages of the bathroom (proximity to water, tile floor, drainage) plus the ability to tailor light and the ability to provide more constant and consistent humidity and a higher than household daytime max temp and a lower than household average nightime min temp. A bathroom windowsill is quite a different thing from a spot inside the shower on a wall though.

H

I have one orchid growing in my bathroom. Its an Igawara (sp?) Apple Blossom. Its doing fine, but I wouldn't try to grow a lot of them in there. It shares the window with a lipstick plant, 2 hoyas, 2 sansevarias, a burros tail succulent, and a marble queen pothos. All are equally happy. This window gets full sun from about 2pm until sundown so light isn't a problem.

I used to grow orchids (Phals and jewels) in my shower, which has skylights, but no windows. They did beautifully along with African violets and Christmas cacti. I'm thinking of moving Paphs there as I'm so good at killing paphs in our very sunny orchid/plant room. Howard is correct about the humidity in a bath not being significant; or sufficient. You'll still need to supplement with pebble trays. I use pea gravel in clear plastic and then in terracotta as the aesthetic of the whole plant is important to me. They would be very challenging to keep up with mounted. A bathroom is not a greenhouse. Although new to this forum I agree with Howard's mantra re: light. If you've got the light, you can usually fix the other stuff (humidity and temp.).

What you might consider is getting two plants and rotating them. While one is in the shower the other is on the windowsill getting the proper light in order to grow.

I actually keep two orchids on the windowsill in my shower stall. It is an east/south window, and I also have two nepenthes there as well. The two orchids are a Phal. Altria, and a Bl. Yellow Bird. They have been in there for over a year now, and the phal is currently blooming two spikes, while the Bl. is putting up two as well, with three flowers each. They actually get tons of humidity, since they're getting watered once a week and "sprayed" twice a day. I actually have to take them out occasionally so their feet don't sog out. They are VERY happy there, right on the sill.

I'm surprised that the phal and the cattleya will both bloom in the same light.

I cant keep orchids drom drying out so i keep them on my bathtub lots if light when they flowered i would move to kitchen to enjoy then return to bathroom but they would still dry out snd lose leaves desperate i moved them inside shower in floor glass block tile lets light in they are so green and happy and have so many firm leaves and air roots now Im editing to answer that mine drain well are in shower floor, it is a large showe bit they gwt hit with fairly direct spray and cast off water and soaps absolutely no issues i make sure to rinse well if suds are visible i startes this practice to really use dr bronner peopermint for gnats in other house plants and regular showers and washings and it worked very well

I had great, great, great results growing orchids in my bathroom in a previous location. I had a whole wall of orchids--the light coming in through the rather small window was just perfect. So a shower/bathroom is not categorically a bad place to grow an orchid. My mind is focusing on the OP's question about growing the orchids "IN" the shower--and my main concern there would be, the actual shower is a place where many chemicals are used that might not jive with a plant. Soaps, shampoos, etc. Even small amounts of these might be harmful to the plant. I don't know about the configuration you are contemplating so maybe this is a non-issue. But apart from that, if you have the right environment it should make no difference to an orchid if it's a shower or a ledge in the living room.